Mine is a Barkers siren and it was great to hear it again after 12 months silence!!! They make a hell of a whoop too! On 180 psi if you're blowing off they will fire up instantly. My favourite toy on the engine. My wife on the other hand cant stand them and last Friday when she came back from her fathers across the road ahe knew we had fired it up cos she heard it and passed a comment that she was dismayed to see it re-instated No pleasing some people

Thanks for posting the picture, I noticed you have a male/female adapter to connect the siren to the cylinder block, was this provided by Barkers, or did you have to buy it? If so, what type of thread/size is it?

If the siren is like mine then it should be threaded 1/4 BSP. This then needs a simple bush 1/4 BSP to 1/4 BSP which is readily available from any plumbers supply. 1/4 BSP takes the 10mm copper pipe which is quite popular these days. It will probably come with two olives and nuts but just discard those. If you get really stuk trying to locate let me know and I'll get one and send it you.